Semiconductor device and process for producing the same

Abstract

Improved control over formation of low k air gaps in interlayer insulating films is achieved by plasma pretreatment of the region of the insulating film to be removed. The intended air gap region is exposed through a mask while the film region to be preserved is shielded by the mask. The intended air gap region is then exposed to a plasma so as to render it more susceptible to removal in a subsequent treatment. One or more Cu interconnects are embedded in both regions of the insulator film. The insulator film in the intended air gap region is then selectively removed to form air gaps adjacent a Cu interconnect in that region.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a method for fabricating a semiconductor device and to the semiconductor device thus made.[0002]The operating speed of various semiconductor devices can be limited by signal propagation delay through interconnects in the devices. The delay constant of an interconnect is a function of the interconnect resistance multiplied by the capacitance between interconnects. A reduction in capacitance between interconnects can therefore improve the operating speed of such devices.[0003]As chip sizes continue to decrease, lower-layer interconnects must be formed at ever-decreasing smaller pitches. Accordingly, high capacitance between lower-layer interconnects is causing significant problems such as crosstalk between interconnects and an increase in power consumption due to an increase in transistor parasitic capacitance.[0004]A low-resistance interconnection technique, the so-called damascene method, is being widely used to form ...

AI Technical Summary

Benefits of technology

[0017]According to the present invention, particular regions of an insulator film are covered with a mask film and regions that are not covered with the mask film are selectively processed by plasma processing. This can increase the etching rate of the insulator film in the regions processed by the plasma relative to the regions not processed by the plasma. Accordingly, the insulator film can be selectively removed from the regions processed by the plasma to form air gaps while the insulator film can be left in the regions where mechanical strength is required. Consequently, a semiconductor device capable of high-speed operation can be fabricated with a high yield.

Problems solved by technology

The operating speed of various semiconductor devices can be limited by signal propagation delay through interconnects in the devices.

Accordingly, high capacitance between lower-layer interconnects is causing significant problems such as crosstalk between interconnects and an increase in power consumption due to an increase in transistor parasitic capacitance.

However, the present inventors have found the following problems with these conventional techniques.

Even more, if air gaps in the insulator film between lower-layer interconnects are too large, the mechanical strength of the interconnects becomes insufficient.

The pressure can cause a problem such as pattern collapse in an interconnect immediately below the solder bumps or bonding wires.

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